ICDs and Pacemakers
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ICD With Leads Into the Heart
Implantable Cardioverter Defibrillators

ICDs are used in patients who experience recurrent rapid or erratic heart rates (tachycardias or fibrillation) or, less frequently, slow heart rates (bradycardias). They are programmed to detect a life threatening heart rhythm and will emit an electrical impulse that will shock the heart to restore normal rhythm when necessary and may even occasionally act as pacemakers.

The ICD device is attached to leads that are implanted in or on the surface of the heart itself. These leads connect to a pulse generator, which is placed in a small pouch (about the size of a PDA or palm pilot) under the skin of the patient's abdomen or chest. This device even keeps records of the heart's activity in the form of ECGs, which can be studied by the patient's physician.

The implantation of the leads inside the heart is generally achieved by non-surgical techniques in which the wires are fed to the heart through blood vessels. The defibrillator will be programmed to meet the individual patient's needs at the time of implantation. During follow-up visits, the information recorded by the device will be downloaded and studied and minor adjustments to the pulse generator will be made if necessary. This downloading procedure involves placing a sensor over the device and is completely painless.

The implantation procedure usually takes about an hour, during which the patient will receive a sedative and may be put to sleep. In most cases, a small incision is made to the collarbone to gain access to the vein through which the leads will pass to the heart (in some cases, the access point will be in the abdominal area).

The degree to which the actions of the ICD are felt by the patient depends on the nature of the impulses that are required. Pacemaking for regular heartbeats that are moderately rapid (tachycardia) or slow (bradycardia) require impulses that are not felt at all or produce the sensation of a mild fluttering around the heart. In cases where the heartbeat is regular but very fast, the ICD will need to produce impulses (cardioversion) that are experienced like a "thump" in the chest. If the pulse becomes irregular and/or very fast (ventricular fibrillation or ventricular tachycardia), the ICD may have to generate a powerful shock. The patient may become unconscious when the heart's rhythm becomes disturbed. If not, then the ICD's impulse may be felt as an uncomfortable "kick" or jolt. However, this will last for only about a second and may save the patient's life.

It is important to let your cardiologist know that your ICD has discharged.